- Email: [email protected]
Cleavage of kininogen and subsequent bradykinin release by MASP-1
Abstracts / Molecular Immunology 46 (2009) 2818–2871
A negative correlation was found between MM2A and attack number recorded in the year of blood sampling (Spearman’s r = −0.2212, p = 0.0241). Spontaneous activation of MBL-MASP2 is not substantial in HAE patients, because MM2A is not decreased. The consumption of C4 results from the activation of C1, primarily. Importantly, the capability of the AA and AB genotypes of MBL-MASP2 is identical for cleaving C4. doi:10.1016/j.molimm.2009.05.264 OP79 Mannose-binding lectin complement pathway plays a key role in complement activation by Paracoccidioides brasiliensis夽 Renan G. Toledo a,∗ , Wilmar D. da Silva a , Vera L.G. Calich b , Thereza L. Kipnis a a
Centro de Biociências e Biotecnologia, Universidade Estadual do Norte Fluminense, RJ, Brazil b Departamento de Imunologia, Instituto de Ciências Biomédicas, Universidade de São Paulo, SP, Brazil Paracoccidioides brasiliensis (Pb) accounts for paracoccidioidomycosis. We have previously reported that Pb activates complement through the alternative pathway (AP) and becomes opsonized. We, herein, demonstrate that dispersed Pb18 (high virulence), when incubated with Normal human serum (NHS) induces consumption of hemolytic complement and, when immobilized, promotes binding of C4b, C3b and C5b-C9. Consumption of components C4, C3 and mannose-binding lectin (MBL) was also verified in MBL-sufficient, but not in MBL-deficient, serum pretreated with dispersed Pb265 (low virulence) or Pb18 (high virulence). When residual complement components were quantified, by deposition on immune-complexes or mannan, consumption of C4, C3 and mannose-binding lectin (MBL) were observed in MBL-sufficient, but not in MBL-deficient, serum pretreated with dispersed Pb265 (low virulence) or Pb18 (high virulence). Higher complement component consumption was observed in serum pretreated with Pb265, as compared with Pb18. The higher complement-activating property exhibited by low virulent strains, was further investigated by comparing the complement activating properties of Pb265 and Pb18(94), two low virulence strains, with the high virulence strain, Pb18. After treating samples of MBL-sufficient serum with various amounts of dispersed fungus, residual C4, the key component of the classical pathway (CP) and lectin pathway (LP) was evaluated by C4c deposition on coated human IgG. Higher C4 consumption was observed in serum samples pretreated with low virulence Pb strains. In addition, data demonstrate that, although attenuated, Pb18 acquires a substantial ability to activate complement, as also evaluated by C4c deposition on coated human IgG. Pb18’s reactivated counter-part simultaneously reacquires virulence, while loosing its complement activating property. Results suggest that non-virulent Pb strains interact more efficiently with MBL, activating MASPs and organizing C4bC2b complexes, with consequent cleavage of C3 and release of C3a and C3b. 夽 “In
Memoriam” to Thereza L. Kipnis*, a dedicated Immunology Professor who developed active research programs that engaged students. doi:10.1016/j.molimm.2009.05.265
2847
OP80 An immunoassay for the assessment of total alternative pathway activity N. de Forest ∗ , J. DeTorres, D. Baker, C. Duncan, N. Nasser Specialty Products Group (SPG), Quidel Corporation, San Diego, CA, United States The binding of C3 or C3b to activating substances triggers the alternative complement pathway. This activation results in a cascade of enzymatic and non-enzymatic reactions, culminating in the formation of terminal complement complexes (TCC). The level of TCC that can be generated in a serum is a quantitative expression of the serum’s total alternative pathway activity. The traditional method for measuring the alternative complement pathway activity in serum is the AH50 hemolytic assay, which uses rabbit erythrocytes (Er) as the activator of the alternative complement pathway and various dilutions of the test serum to determine the amount required to give 50% lysis. The traditional, hemolytic AH50 test is an indirect measure of TCC, since the TCC themselves are directly responsible for the hemolysis being measured. The AH50 Eq EIA provides a direct measure of the alternative complement activity in serum by quantifying the amount of TCC generated. The specimen is activated with the activator and then the amount of TCC generated is measured. The AH50 Eq EIA uses a monoclonal antibody specific to a unique neoantigen on C9 to capture the TCC analyte. The assay has a lower limit of quantitation of 3.0 AH50 U Eq/ml, a lower limit of quantitation of 5.03 AH50 U Eq/ml and an upper limit of quantitation of 306 AH50 U Eq/ml. Within-run and between-run precision was determined to have a coefficient of variation (%CV) is 5.2% and 11.7%, respectively. The correlation with the traditional hemolytic assay has been shown to be >97%. The AH50 Eq EIA is an improvement on the traditional hemolytic assay. It eliminates the need to prepare standardized red blood cells and the shelf life and inter-lot performance are limited and unpredictable in the traditional method. The results generated by the AH50 Eq EIA are sensitive, standardized and quantitative. doi:10.1016/j.molimm.2009.05.266 OP81 Cleavage of kininogen and subsequent bradykinin release by MASP-1 József Dobó a,∗ , Balázs Major a , Katalin A. Kékesi b , István Szabó a , Gábor Juhász c , Péter Závodszky a , Péter Gál a a
Institute of Enzymology, Biological Research Center, Hungarian Academy of Sciences, Karolina út 29, H-1113, Budapest, Hungary b Department of Physiology and Neurobiology, Eötvös Loránd University, Pázmány Péter sétány 1C, H-1117, Budapest, Hungary c Laboratory of Proteomics, Institute of Biology, Eötvös Loránd University, Pázmány Péter sétány 1C, H-1117, Budapest, Hungary Mannose-binding lectin (MBL)-associated serine protease-1 (MASP-1) is an abundant component of the lectin pathway of complement. The related enzyme, MASP-2 is capable of activating the complement cascade alone. Though the concentration of MASP-1 far exceeds that of MASP-2 only a supporting role of MASP-1 has been identified regarding lectin pathway activation. Several noncomplement substrates, like fibrinogen and factor XIII, have also been reported. We have investigated the action of activated MASP-1 on plasma proteins using a recombinant truncated form (rMASP-1) encompassing the last three domains (CCP1–CCP2–SP), and human
2848
Abstracts / Molecular Immunology 46 (2009) 2818–2871
plasma depleted from seven abundant proteins. Analysis by 2D gel electrophoresis and protein identification by mass spectroscopy revealed a kininogen cleavage product. Cleavage of high molecular weight kininogen (HK) was later confirmed by SDS-PAGE analysis using purified proteins. The cleavage pattern of HK by rMASP-1 is similar but somewhat different from that of by plasma kallikrein (PK). The fastest cleavage seems to occur within the L chain portion of HK by rMASP-1 and the release of the H chain occurs slower, whereas PK cleaves HK producing the H and L chains rapidly then the L chain is slowly converted into smaller fragments. The final stable products seem to be the same by both proteases. The cleavage of HK by rMASP-1 is about 20 times slower than that of HK by PK based on the kcat /KM values determined from densitometric analysis. The reaction mixture of rMASP-1 and HK analysed by HPLC produced a peak eluting at the same position as the bradykinin standard. The peak contained a species having the molecular weight of 1060 Da, which is identical to that of bradykinin. Hence we conclude that rMASP-1 and possibly activated full length MASP-1 in blood can lead to the breakdown of HK and bradykinin formation. Bradykinin is the major mediator of tissue swelling during the attacks of patients suffering from hereditary angiooedema (HAE), a disease mainly caused by C1-inhibitor deficiency. C1-inhibitor is the major inhibitor of PK and also inhibits MASP-1. The physiological importance of HK cleavage by MASP-1 is unknown, but we can speculate that under certain conditions (like infection) it may cause the worsening of the symptoms of HAE patients. doi:10.1016/j.molimm.2009.05.267 OP82 Systemic and intrathecal complement activation in multiple sclerosis and Guillan-Barré syndrome Kristina N. Ekdahl a,b,∗ , Carolina Blomberg a , Anna J. Henningsson c , Charlotte Dahle d , Irene Håkansson e , Kerstin Sandholm a , Jan Ernerudh d a
School of Pure and Applied Natural Sciences, Kalmar University, Kalmar, Sweden b Division of Clinical Immunology, Rudbeck Laboratory, University hospital, Uppsala, Sweden c Department of Infectious Diseases, Ryhov County Hospital, Jönköping, Sweden d Department of Clinical Experimental Medicine, Div of Clinical Immunology, Linköping, Sweden e Department of Clinical Experimental Medicine, Div of Neurology, Linköping, Sweden Background: Multiple sclerosis (MS) and Guillain-Barré syndrome (GBS) are two inflammatory demyelinating diseases which affect the central and the peripheral nervous system, respectively. Complement activation has been implicated as a deleterious factor in both conditions, but the mechanisms by which complement activation causes tissue damage are incompletely understood. Aim: The overall aim of this study is to explore systemic and intrathecal complement activation in MS and GBS. Patients and Methods: EDTA plasma and cerebrospinal fluid (CSF) were collected from 48 patients with MS, 8 patients with GBS, and 19 healthy controls. The levels of C1q, C3, C3a, C4 and factor H (FH) were analyzed by sandwich ELISAs. Complement activation was evaluated by calculating the ratio between C3a and C3 to compensate for variations in C3 concentration since C3 is an acute phase protein. Results: In MS, the levels of C1q, C4 and FH in plasma did not differ from those found in controls, but the concentrations of C3 and
C3a were significantly increased in MS plasma. The degree of activation, i.e., monitored as the C3a/C3 ratio, indicated an increased systemic complement activation. Normal levels of all measured complement components and activation products were found in CSF from MS patients. Normal levels of complement components and C3a were detected in plasma from GBS patients. However, in contrast to MS, increased C3a/C3 ratio was found in CSF from GBS patients. In CSF from GBS a positive correlation was found between the (increased) levels of C1q and C3a, suggesting that complement activation may be triggered by the classical pathway. However, data need to be reconsidered taking in account the albumin ratio reflecting blood to CSF passage. Conclusions: Our data suggest that the complement system is activated in the CNS in GBS. In contrast, systemic activation is seen in MS. doi:10.1016/j.molimm.2009.05.268 OP83 MASP2 and MBL2 gene polymorphisms in a Brazilian population N.R. Ferraroni a , S. Crovella S b,c , R.L. Guimarães c , L.A.C. Brandão c , C. Alves a , L. Segat b,c , R.N. Constantino-Silva a , I.M. Siqueira d , C. Loja d , A.J.S. Duarte a , A.S. Grumach a,∗ a
Laboratory of Dermatology and Immunodeficiencies, Department of Dermatology, Faculty of Medicine, University of São Paulo, São Paulo, Brazil b Genetic Service and Department of Developmental and Reproductive Sciences, IRCCS Burlo Garofolo and University of Trieste, Trieste, Italy c Department of Genetics, Federal University of Pernambuco, Recife, Brazil d Hospital dos Servidores do Estado do Rio de Janeiro, Rio de Janeiro, Brazil
E-mail address: [email protected] (A.S. Grumach). Mannose-binding lectin (MBL) is a protein that recognizes carbohydrates on microbial surfaces leading to complement activation mediated by associated serine proteases, named MASPs (1, 2 and 3). MASP2, in particular, is responsible to generate the C3 convertase C4bC2b. Both MBL and MASP2 levels are genetically determined, and can be influenced by the presence of single nucleotide polymorphisms (SNPs) in the genes encoding for these proteins (MBL2 and MASP2, respectively). Aim: to determine the frequencies of MBL2 and MASP2 gene polymorphisms in a Brazilian population, since only few data are available so far. Methods: 300 blood donor samples were genotyped for MBL2 exon 1 SNPs (single point mutation in codon 54 (GGC to GAC), in codon 57 (GGA to GAA) and in codon 52 (CGT to TGT)) and MASP2 rs12711521 polymorphism (in exon 9). A melting temperature assay was used to perform the genotyping of MBL2 SNPs. The combination of variants of MBL2 were grouped together as allele O; wild types were indicated as A. MASP2 exon 9 genotyping was performed by using TaqMan pre-developed assay. The median age of individuals was 37 years (range 18–63), 87/300 (29%) females and 213/300 (71%) males. Results: the frequencies of MBL2 exon 1 SNPs genotypes were 58.7% A/A (176/300), 34.7% A/O (104/300) and 6,7% O/O (20/300). The frequencies of MASP2 genotypes were 39% A/A (117/300), 44% A/C (132/300) and 17% C/C (51/300). The allelic frequencies were A = 76%, O = 24% for MBL2 and A = 61%, C = 39% for MASP2. In conclusion, the prevalence (6.7%) of O/O genotypes of MBL2 exon 1 SNPs in Brazilians was higher than Europeans (Danish and British 4%), lower than Sub-Saharan Africans from East and West
A negative correlation was found between MM2A and attack number recorded in the year of blood sampling (Spearman’s r = −0.2212, p = 0.0241). Spontaneous activation of MBL-MASP2 is not substantial in HAE patients, because MM2A is not decreased. The consumption of C4 results from the activation of C1, primarily. Importantly, the capability of the AA and AB genotypes of MBL-MASP2 is identical for cleaving C4. doi:10.1016/j.molimm.2009.05.264 OP79 Mannose-binding lectin complement pathway plays a key role in complement activation by Paracoccidioides brasiliensis夽 Renan G. Toledo a,∗ , Wilmar D. da Silva a , Vera L.G. Calich b , Thereza L. Kipnis a a
Centro de Biociências e Biotecnologia, Universidade Estadual do Norte Fluminense, RJ, Brazil b Departamento de Imunologia, Instituto de Ciências Biomédicas, Universidade de São Paulo, SP, Brazil Paracoccidioides brasiliensis (Pb) accounts for paracoccidioidomycosis. We have previously reported that Pb activates complement through the alternative pathway (AP) and becomes opsonized. We, herein, demonstrate that dispersed Pb18 (high virulence), when incubated with Normal human serum (NHS) induces consumption of hemolytic complement and, when immobilized, promotes binding of C4b, C3b and C5b-C9. Consumption of components C4, C3 and mannose-binding lectin (MBL) was also verified in MBL-sufficient, but not in MBL-deficient, serum pretreated with dispersed Pb265 (low virulence) or Pb18 (high virulence). When residual complement components were quantified, by deposition on immune-complexes or mannan, consumption of C4, C3 and mannose-binding lectin (MBL) were observed in MBL-sufficient, but not in MBL-deficient, serum pretreated with dispersed Pb265 (low virulence) or Pb18 (high virulence). Higher complement component consumption was observed in serum pretreated with Pb265, as compared with Pb18. The higher complement-activating property exhibited by low virulent strains, was further investigated by comparing the complement activating properties of Pb265 and Pb18(94), two low virulence strains, with the high virulence strain, Pb18. After treating samples of MBL-sufficient serum with various amounts of dispersed fungus, residual C4, the key component of the classical pathway (CP) and lectin pathway (LP) was evaluated by C4c deposition on coated human IgG. Higher C4 consumption was observed in serum samples pretreated with low virulence Pb strains. In addition, data demonstrate that, although attenuated, Pb18 acquires a substantial ability to activate complement, as also evaluated by C4c deposition on coated human IgG. Pb18’s reactivated counter-part simultaneously reacquires virulence, while loosing its complement activating property. Results suggest that non-virulent Pb strains interact more efficiently with MBL, activating MASPs and organizing C4bC2b complexes, with consequent cleavage of C3 and release of C3a and C3b. 夽 “In
Memoriam” to Thereza L. Kipnis*, a dedicated Immunology Professor who developed active research programs that engaged students. doi:10.1016/j.molimm.2009.05.265
2847
OP80 An immunoassay for the assessment of total alternative pathway activity N. de Forest ∗ , J. DeTorres, D. Baker, C. Duncan, N. Nasser Specialty Products Group (SPG), Quidel Corporation, San Diego, CA, United States The binding of C3 or C3b to activating substances triggers the alternative complement pathway. This activation results in a cascade of enzymatic and non-enzymatic reactions, culminating in the formation of terminal complement complexes (TCC). The level of TCC that can be generated in a serum is a quantitative expression of the serum’s total alternative pathway activity. The traditional method for measuring the alternative complement pathway activity in serum is the AH50 hemolytic assay, which uses rabbit erythrocytes (Er) as the activator of the alternative complement pathway and various dilutions of the test serum to determine the amount required to give 50% lysis. The traditional, hemolytic AH50 test is an indirect measure of TCC, since the TCC themselves are directly responsible for the hemolysis being measured. The AH50 Eq EIA provides a direct measure of the alternative complement activity in serum by quantifying the amount of TCC generated. The specimen is activated with the activator and then the amount of TCC generated is measured. The AH50 Eq EIA uses a monoclonal antibody specific to a unique neoantigen on C9 to capture the TCC analyte. The assay has a lower limit of quantitation of 3.0 AH50 U Eq/ml, a lower limit of quantitation of 5.03 AH50 U Eq/ml and an upper limit of quantitation of 306 AH50 U Eq/ml. Within-run and between-run precision was determined to have a coefficient of variation (%CV) is 5.2% and 11.7%, respectively. The correlation with the traditional hemolytic assay has been shown to be >97%. The AH50 Eq EIA is an improvement on the traditional hemolytic assay. It eliminates the need to prepare standardized red blood cells and the shelf life and inter-lot performance are limited and unpredictable in the traditional method. The results generated by the AH50 Eq EIA are sensitive, standardized and quantitative. doi:10.1016/j.molimm.2009.05.266 OP81 Cleavage of kininogen and subsequent bradykinin release by MASP-1 József Dobó a,∗ , Balázs Major a , Katalin A. Kékesi b , István Szabó a , Gábor Juhász c , Péter Závodszky a , Péter Gál a a
Institute of Enzymology, Biological Research Center, Hungarian Academy of Sciences, Karolina út 29, H-1113, Budapest, Hungary b Department of Physiology and Neurobiology, Eötvös Loránd University, Pázmány Péter sétány 1C, H-1117, Budapest, Hungary c Laboratory of Proteomics, Institute of Biology, Eötvös Loránd University, Pázmány Péter sétány 1C, H-1117, Budapest, Hungary Mannose-binding lectin (MBL)-associated serine protease-1 (MASP-1) is an abundant component of the lectin pathway of complement. The related enzyme, MASP-2 is capable of activating the complement cascade alone. Though the concentration of MASP-1 far exceeds that of MASP-2 only a supporting role of MASP-1 has been identified regarding lectin pathway activation. Several noncomplement substrates, like fibrinogen and factor XIII, have also been reported. We have investigated the action of activated MASP-1 on plasma proteins using a recombinant truncated form (rMASP-1) encompassing the last three domains (CCP1–CCP2–SP), and human
2848
Abstracts / Molecular Immunology 46 (2009) 2818–2871
plasma depleted from seven abundant proteins. Analysis by 2D gel electrophoresis and protein identification by mass spectroscopy revealed a kininogen cleavage product. Cleavage of high molecular weight kininogen (HK) was later confirmed by SDS-PAGE analysis using purified proteins. The cleavage pattern of HK by rMASP-1 is similar but somewhat different from that of by plasma kallikrein (PK). The fastest cleavage seems to occur within the L chain portion of HK by rMASP-1 and the release of the H chain occurs slower, whereas PK cleaves HK producing the H and L chains rapidly then the L chain is slowly converted into smaller fragments. The final stable products seem to be the same by both proteases. The cleavage of HK by rMASP-1 is about 20 times slower than that of HK by PK based on the kcat /KM values determined from densitometric analysis. The reaction mixture of rMASP-1 and HK analysed by HPLC produced a peak eluting at the same position as the bradykinin standard. The peak contained a species having the molecular weight of 1060 Da, which is identical to that of bradykinin. Hence we conclude that rMASP-1 and possibly activated full length MASP-1 in blood can lead to the breakdown of HK and bradykinin formation. Bradykinin is the major mediator of tissue swelling during the attacks of patients suffering from hereditary angiooedema (HAE), a disease mainly caused by C1-inhibitor deficiency. C1-inhibitor is the major inhibitor of PK and also inhibits MASP-1. The physiological importance of HK cleavage by MASP-1 is unknown, but we can speculate that under certain conditions (like infection) it may cause the worsening of the symptoms of HAE patients. doi:10.1016/j.molimm.2009.05.267 OP82 Systemic and intrathecal complement activation in multiple sclerosis and Guillan-Barré syndrome Kristina N. Ekdahl a,b,∗ , Carolina Blomberg a , Anna J. Henningsson c , Charlotte Dahle d , Irene Håkansson e , Kerstin Sandholm a , Jan Ernerudh d a
School of Pure and Applied Natural Sciences, Kalmar University, Kalmar, Sweden b Division of Clinical Immunology, Rudbeck Laboratory, University hospital, Uppsala, Sweden c Department of Infectious Diseases, Ryhov County Hospital, Jönköping, Sweden d Department of Clinical Experimental Medicine, Div of Clinical Immunology, Linköping, Sweden e Department of Clinical Experimental Medicine, Div of Neurology, Linköping, Sweden Background: Multiple sclerosis (MS) and Guillain-Barré syndrome (GBS) are two inflammatory demyelinating diseases which affect the central and the peripheral nervous system, respectively. Complement activation has been implicated as a deleterious factor in both conditions, but the mechanisms by which complement activation causes tissue damage are incompletely understood. Aim: The overall aim of this study is to explore systemic and intrathecal complement activation in MS and GBS. Patients and Methods: EDTA plasma and cerebrospinal fluid (CSF) were collected from 48 patients with MS, 8 patients with GBS, and 19 healthy controls. The levels of C1q, C3, C3a, C4 and factor H (FH) were analyzed by sandwich ELISAs. Complement activation was evaluated by calculating the ratio between C3a and C3 to compensate for variations in C3 concentration since C3 is an acute phase protein. Results: In MS, the levels of C1q, C4 and FH in plasma did not differ from those found in controls, but the concentrations of C3 and
C3a were significantly increased in MS plasma. The degree of activation, i.e., monitored as the C3a/C3 ratio, indicated an increased systemic complement activation. Normal levels of all measured complement components and activation products were found in CSF from MS patients. Normal levels of complement components and C3a were detected in plasma from GBS patients. However, in contrast to MS, increased C3a/C3 ratio was found in CSF from GBS patients. In CSF from GBS a positive correlation was found between the (increased) levels of C1q and C3a, suggesting that complement activation may be triggered by the classical pathway. However, data need to be reconsidered taking in account the albumin ratio reflecting blood to CSF passage. Conclusions: Our data suggest that the complement system is activated in the CNS in GBS. In contrast, systemic activation is seen in MS. doi:10.1016/j.molimm.2009.05.268 OP83 MASP2 and MBL2 gene polymorphisms in a Brazilian population N.R. Ferraroni a , S. Crovella S b,c , R.L. Guimarães c , L.A.C. Brandão c , C. Alves a , L. Segat b,c , R.N. Constantino-Silva a , I.M. Siqueira d , C. Loja d , A.J.S. Duarte a , A.S. Grumach a,∗ a
Laboratory of Dermatology and Immunodeficiencies, Department of Dermatology, Faculty of Medicine, University of São Paulo, São Paulo, Brazil b Genetic Service and Department of Developmental and Reproductive Sciences, IRCCS Burlo Garofolo and University of Trieste, Trieste, Italy c Department of Genetics, Federal University of Pernambuco, Recife, Brazil d Hospital dos Servidores do Estado do Rio de Janeiro, Rio de Janeiro, Brazil
E-mail address: [email protected] (A.S. Grumach). Mannose-binding lectin (MBL) is a protein that recognizes carbohydrates on microbial surfaces leading to complement activation mediated by associated serine proteases, named MASPs (1, 2 and 3). MASP2, in particular, is responsible to generate the C3 convertase C4bC2b. Both MBL and MASP2 levels are genetically determined, and can be influenced by the presence of single nucleotide polymorphisms (SNPs) in the genes encoding for these proteins (MBL2 and MASP2, respectively). Aim: to determine the frequencies of MBL2 and MASP2 gene polymorphisms in a Brazilian population, since only few data are available so far. Methods: 300 blood donor samples were genotyped for MBL2 exon 1 SNPs (single point mutation in codon 54 (GGC to GAC), in codon 57 (GGA to GAA) and in codon 52 (CGT to TGT)) and MASP2 rs12711521 polymorphism (in exon 9). A melting temperature assay was used to perform the genotyping of MBL2 SNPs. The combination of variants of MBL2 were grouped together as allele O; wild types were indicated as A. MASP2 exon 9 genotyping was performed by using TaqMan pre-developed assay. The median age of individuals was 37 years (range 18–63), 87/300 (29%) females and 213/300 (71%) males. Results: the frequencies of MBL2 exon 1 SNPs genotypes were 58.7% A/A (176/300), 34.7% A/O (104/300) and 6,7% O/O (20/300). The frequencies of MASP2 genotypes were 39% A/A (117/300), 44% A/C (132/300) and 17% C/C (51/300). The allelic frequencies were A = 76%, O = 24% for MBL2 and A = 61%, C = 39% for MASP2. In conclusion, the prevalence (6.7%) of O/O genotypes of MBL2 exon 1 SNPs in Brazilians was higher than Europeans (Danish and British 4%), lower than Sub-Saharan Africans from East and West